Self-starting timing escapement



J1me 1965 R. 1.. ARCHER ETAL 3,186,238

SELF-STARTING TIMING ESCAPEMENT Filed April 29, 1963 FIG.3

United States. Patent l This invention relates to self-starting timing escapements and is of general application to Watches, clocks, and

various mechanical and electromechanical timing mechanisms.

In general, escapement mechanisms have been of two principal types, generally known as the attached lever and the detached lever types, which terms refer to the physical interaction between the oscillating assembly and other parts of the escapement. In the attached lever type, there is a continuous engagement between the oscillating assembly and other parts, such as the crutch, pallet, cylinder, or verge, during the entire range of oscillation, such attachment tending to damp its free oscillation. Detached lever escapements include, in general, an escapement wheel, a mechanical resonant oscillating assembly, usually a balance wheel and hairspring, and a pivoted pallet interconnecting the two. In such detached type, the oscillating assembly is engaged only during the balance arc, that is, the portion of the oscillatory movement during which energy is transferred to or from the oscillating assembly. During the remainder of the oscillatory movement, the oscillation of the assembly is free.

While the attached type of timing escapement described may be inherently self-starting, the detached type is not. That is, if the driving force is removed from the escapement, for example if the mainspring becomes unwound or if the oscillating element is externally interfered with, the oscillating assembly can stop in such a position that, when the driving force is restored or the physical interference is removed, the escapement will not automatically restart but may require external aid such as mechanical oscillation or vibration. While external movement of the timing mechanism, such as in a wrist watch, is usually sufiicient to initiate movement of the oscillation system, this is not certain and, in timing devices forming an integral part of a stationary mechanism, this automatic restarting ordinarily will not occur. This lack of selfstarting capability is, in general, due to the fact that the teeth of the escapement wheel form a negative locking angle with the pallet pins, creating a moment on the pallet which draws the pins into deeper engagement with the escapement wheel, so that the oscillating assembly must have sutlicient momentum when its impulse pin strikes the pallet slot to pull the engaged pallet pin out of its locked position and flip it to the impulse face on the tooth. This face will then force the pallet to the next tooth. Moreover, in such an escapement mechanism in its stopped position, the oscillating assembly is displaced from its dead-center position by one-half of the balance are. In either extreme position of the pallet, the force applied to the escapement wheel produces a moment about the pallet pivot tending to draw the pallet pin into deeper engagement with the escapement wheel and still further impeding the oscillating assembly from achieving dead-center position, that is, the force is in a sense opposite to that required to initiate oscillation of the system. It would obviously be desirable that the timing escapement mechanism be inherently self-starting with certainty whenever a driving force is applied to the escapement, regardless of pallet position.

It is an object of the invention therefore, to provide a new and improved timing escapement which has the characteristic of automatically starting with certainty whenever a driving force is applied to the escapement wheel.

It isa further object of the invention to provide a new and improved timing escapement of the type described, characterized by a minimum frictional load, thus improving the timing accuracy of the mechanism.

In accordance with the invention, there is provided a self-starting timing escapement comprising a driven escapement wheel, a pivoted pallet slotted at one end and having a pair of spaced driven elements at its other end disposed alternately to engage spaced teeth of the escapement wheel, a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation, an impulse element on the oscillating assembly disposed to engage the pallet slot during the balance are thereof and to move beyond and disengage the pallet slot at both extremes of oscillation of the assembly, a circular lockout element movable with the oscillating assembly and having a peripheral recess of an extent substantially equal to the balance are and centered about the dead-center position thereof, and an element mounted on the pallet and normally biased into engagement with the lockout element during the portions of the oscillation of the assembly when the impulse element and the pallet slot are disengaged.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description, taken in connection with the accompanying drawing, while its scope will be pointed out in the appended claims;

Referring to the drawing:

FIG. 1 is a plan view of a self-starting timing escapement embodying the invention showing the relative positions of the elements in one extreme limit of movement of the oscillating assembly;

FIG. 2 is a plan view of the apparatus of FIG. 1 showing the relative positions of the elements in the deadcenter position of the oscillating assembly, while FIG. 3 is a plan view of the apparatus of FIG. 1 showing the relative positions of the elements with the oscillating assembly in its other extreme limit of movement.

Referring now more patricularly to FIG. 1 of the drawing, there is represented a self-starting timing escapement embodying the invention and comprising an escapement wheel 16 driven by a spring or other conventional power source, not shown. Each of the teeth of the escapement wheel 15 has duplicate impulse faces mirrored about a line of symmetry in each tooth such that action can start regardless of the sense of application of the driving force on the escapement wheel. For example, considering tooth ltla, it is seen that its two active faces 10b, 10c are mirror images about a line of symmetry 10d. Cooperating with the wheel 10 is a pallet 11 mounted on a pivot pin 12 and having at one end a slot 11a. The other end of the pallet 11 is forked and carries, at the forked ends, a pair of spaced driven elements or pins 13, 14. The relative disposition of parts is such that, in the operation of the escapement, the driven pins 13, 14 alternately engage spaced teeth of the escapement wheel 16.

The escapement of the invention further comprises a rotatable mechanical oscillating assembly, specifically a balance wheel 15 and hairspring 16 mounted for'oscillation about a pivot shaft 17. The balance wheel 15 and spring 16 are designed to have a predetermined natural period of oscillation in a well-known manner. The assembly 15, 16 includes an impulse element or pin 18 disposed to engage the slot 11a of the pallet 11 during the balance are of the assembly.

The escapement of the invention further comprises a circular lockout element or safety roller 19 unitary with and movable with the oscillating assembly and having a peripheral arcuate recess 20 of an extent substantially equal to the balance are of the assembly and centered about the dead-center position thereof. Mounted on the pallet 11 is an element, such as an anti-friction roller 21, normally biased into engagement with the lockout element 19 in both extreme stable positions of the escapement mechanism. Limit or stop pins 22, 22 are disposed on either side of pallet 11 although, in normal opera-tion, they are not engaged by the pallet.

It is believed that the operation of the escapement of the invention will be apparent from the foregoing description. In the position of the elements shown in FIG. '1, representing the extreme counterclockwise position of the pallet 11 about its pivot 12, the pin 13 is in engagement with one of the teeth of the escapement wheel 10. The configuration of the tooth surfaces is such that the force, represented by the vector P, acting on the pin 13 at a distance d from its pivot 12 exerts a clockwise moment M on the pallet 11. However, in the relative positions of the parts shown, clockwise motion is prevented by engagement of the roller 21 and the lockout element 19. Nevertheless, the oscillation of the balance wheel is not impeded, due to the anti-friction action of the roller 21. It can be assumed, in this position, that the balance wheel 15 is in its extreme position clockwise. Upon its return swing, the impulse pin 18 engages the slot 11a of the pallet 11 and, upon such engagement, the roller 21 enters the recess 20, permitting a clockwise motion of the pallet 11 about its pivot 12 under the influence of force F and camming the pin 13 from the tooth of the wheel 10. This motion continues until the several elements occupy the positions shown in FIG. 2 in which the pallet 11 is approximately on dead center. It is seen that, in this position, the moment of the force F, acting on the pin 13 through the distance d from the pivot 12, still exerts a clockwise moment M on the pallet 11 so that it continues to impart energy to the balance wheel 15 through the engagement with the pin 18.

As the pin 13 disengages the tooth of the wheel 10, the pin 14 engages a spaced tooth thereof but the configuration of the teeth of the escapement wheel 11 is such that now the force F, acting on the pin 14 through a distance d on the other side of the pivot 12, exerts a counterclockwise moment M on the pallet 11, tending to move it towards its dead-center position. It is assumed that FIG. 3 represents the counterclockwise extreme position of the balance wheel 15. Thus, in this extreme position also, the escapement wheel 10 exerts a moment on the pallet 11 acting to move it toward deadcenter position. As in the position represented by FIG. 1 however, such movement of the pallet 11 is prevented by the engagement of the roller 21 with the lockout element 19.

Stated another way, in contrast to conventional escapement mechanisms in which the driven pallet pins tend to lock into engagement with the teeth of the escapement Wheel in both extreme positions and are dislodged therefrom by the impulse developed upon engagement of the impulse pin of the balance wheel with the pallet slot, in the escapement mechanism of the invention the configuration of the escapement wheel is such that, in both extreme positions of the pallet, the force exerted on the driven elements 13, 14 is in a direction tending to eject them from engagement with the teeth of the escapement wheel.

If for any reason the escapement mechanism of the in veution stops, as by an unwinding of the spring driving the escapement wheel 10 or by physical interference with the balance wheel 15, the mechanism will stop in any position, such as one of the positions shown in FIGS. 1, 2, and 3. Upon re-application of a force F by the escapement wheel 10, as by winding, or upon removal of the external interference, the pallet 11 is always under a properly directed torque which is transmitted by the pallet and the impulse pin 18 immediately and automatically to initiate an oscillation of the oscillating assembly 1 4: 15, 16. That is, the escapement mechanism of the inyention is always automatically self-starting.

,While there has been described what is, at present, considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein, without departing from the invention and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A self-starting timing escapement comprising:

(a) a driven escapement wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaced driven elements at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation;

(d) an impulse element on said assembly disposed to engage said pallet slot during the balance are thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent susbtantially equal to said balance are and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout element during the portions of the oscillation of said assembly when said impulse element and said pallet slot are disengaged.

2. A self-starting timing escapement comprising:

(a) a driven escapement wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaced pins at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation;

(d) a pin on said assembly disposed to engage said pallet slot during the balance are thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent substantially equal to said balance are and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout element during the portions of the oscillation of said assembly when said pin and said pallet slot are disengaged.

3. A self-starting timing escapement comprising:

(a) a driven escapement wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaced driven elements at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a balance wheel and hairspring assembly having a predetermined natural period of oscillation;

(d) an impulse element on said assembly disposed to engage said pallet slot during the balance arc thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent substantially equal to said balance are and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout element during the portions of the oscillation of said assembly when said impulse element and said pallet slot are disengaged.

4. A self-starting timing escapement comprising:

(a) a driven escapement wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaced driven elements at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation;

(d) an impulse element on said assembly disposed to engage said pallet slot during the balance are thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent substantially equal to said balance are and centered about the dead-center position thereof; (f) and an anti-friction roller mounted on said pallet and normally biased into engagement with said lock- (d) an impulse element on said assembly disposed to engage said pallet slot during the balance are thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent substantially equal to said balance arc and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout element during the portions of the oscillation of said assembly when said impulse element and said pallet slot are disengaged;

(g) the teeth ofsaid escapement wheel having a configuration such that in both extreme positions of said pallet a moment is exerted on said pallet acting to move it toward dead-center position.

6. A self-starting timing escapement comprising:

(a) a driven escapement wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaced driven elements at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation;

(d) an impulse element on said assembly disposed to engage said pallet slot during the balance are thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent substantially equal to said balance are and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout element during the portions of the oscillation of said assembly when said impulse element and said pallet slot are disengaged;

(g) the teeth of said escapement wheel having duplicate impulse faces mirrored about a line of symmetry in each tooth such that action can start regardless of the sense of application of the driving torque on the escapement wheel.

7. A self-starting timing escapement comprising:

(a) a driven escapement wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaceddriven elements at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation;

(d) an impulse element on said assembly disposed to engage said pallet slot during the balance are thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent susbtantially equal to said balance arc and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout 'element during the portions of the oscillation of said assembly when said impulse element and said pallet slot are disengaged;

(g) the teeth of said .escapement Wheel having a con- 7 figuration such that in both extreme positions of said pallet the force exerted on said driven elements is in a direction to eject said driven elements from the escapement wheel.

8. A self-starting timing escapement comprising:

(a) a driven escapement Wheel;

(b) a pivoted pallet slotted at one end and having a pair of spaced driven elements at its other end disposed alternately to engage spaced teeth of said wheel;

(c) a rotatable mechanical oscillating assembly having a predetermined natural period of oscillation;

(d) an impulse element on said assembly disposed to engage said pallet slot during the balance arc thereof and to move beyond and disengage said pallet slot at both extremes of oscillation of said assembly;

(e) a circular lockout element movable with said assembly and having a peripheral recess of an extent substantially equal to said balance arc and centered about the dead-center position thereof;

(f) and an element mounted on said pallet and normally biased into engagement with said lockout element during the portions of the oscillation of said assembly when said impulse element and said pallet slot are disengaged;

(g) said lockout element being etfective to limit the movement of said pallet toward dead-center position except during engagement of said pallet element and said recess.

References ited by the Examiner UNITED STATES PATENTS 2,647,3 62 3/53 Fidelman 58-117 FOREIGN PATENTS 243, 142 1/ 46 Switzerland.

LEO SMILOW, Primary Examiner.

r JOSEPH P. STRIZAK, Examiner. 

1. A SELF-STARTING TIMING ESCAPEMENT COMPRISING: (A) A DRIVEN ESCAPEMENT WHEEL; (B) A PIVOTED PALLET SLOTTED AT ONE END AND HAVING A PAIR OF SPACED DRIVEN ELEMENTS AT ITS OTHER END DISPOSED ALTERNATELY TO ENGAGE SPACED TEETH OF SAID WHEEL; (C) A ROTATABLE MECHANICAL OSCILLATING ASSEMBLY HAVING A PREDETERMINED NATURAL PERIOD OF OSCILLATION; (D) AN IMPULSE ELEMENT ON SAID ASSEMBLY DISPOSED TO ENGAGE SAID PALLET SLOT DURING THE BALANCE ARC THEREOF AND TO MOVE BEYOND AND DISENGAGE SAID PALLET SLOT AT BOTH EXTREMES OF OSCILLATION OF SAID ASSEMBLY; (E) A CIRCULAR LOCKOUT ELEMENT MOVABLE WITH SAID ASSEMBLY AND HAVING A PERIPHERAL RECESS OF AN EXTENT SUBSTANTIALLY EQUAL TO SAID BALANCE ARC AND CENTERED ABOUT THE DEAD-CENTER POSITION THEREOF; (F) AND AN ELEMENT MOUNTED ON SAID PALLET AND NORMALLY BIASED INTO ENGAGEMENT WITH SAID LOCKOUT ELEMENT DURING THE PORTIONS OF THE OSCILLATION OF SAID ASSEMBLY WHEN SAID IMPULSE ELEMENT AND SAID PALLET SLOT ARE DISENGAGED. 